Granite batholiths record the processes that occur during the formation and differentiation of the continental crust. The ~ 4000 km
2
composite Neoproterozoic Jiuling batholith is one of the largest ...batholiths in southern China and consists of four peraluminous granitoid intrusions that were emplaced at
ca.
828–810 Ma. These granitoids define a trend that moves from the terrestrial towards the seawater Nd–Hf isotope array, indicating the source of these magmas incorporated increasing amounts of marine sedimentary material over time. Our new geochronological and geochemical data suggest that the composite Neoproterozoic Jiuling batholith formed incrementally via the intrusion of multiple batches of crustally derived melts. The intrusions within the batholith are characterized by decreasing Rb/Sr ratios and increasing Na/K ratios and ε
Hf
(t) values, suggesting variations in source composition over time. These inter-intrusion variations can be well explained by three-component mixing in magma sources (mature, immature sediments and felsic arc-related granitoids) prior to partial melting, with inter-sample variations within individual intrusions occurring as a result of the subsequent mixing of different melt batches. The first stage of mixing within the source of these magmas involves a significant variation in source compositions and cannot reflect the simple melting of a heterogeneous metasedimentary source region. The second stage of mixing occurred during magma ascent and storage, and is recorded by variations in mineral compositions (e.g., zircon). These inter-intrusion and inter-sample geochemical variations provide evidence that the peraluminous Jiuling batholith formed as a result of two mixing processes, namely mixing within the magma source region and mixing of multiple batches of granitic melts. This dual mixing could explain the significant geochemical diversity present within peraluminous granitoid rocks worldwide.
Abstract
Gas-solid two phase flow widely lies in industry process, while its parameters measurement (flow velocity, the mass flowrate, particle sizes, et al.) is very difficult. This paper mainly ...studies the solid phase flow velocity measurement questions of gas-solid two phase flow with the ring electrostatic sensor. During the flow velocity measurement study, a new mathematical model of the electrostatic sensor is established, and by simulating the obtained model the spatial filter characteristics of the electrostatic sensor are obtained. By the spatial filter characteristics analysis of the ring electrostatic sensor, a new flow velocity measurement method is obtained in this paper. At last, some experiments are accomplished in the laboratory with line sand. The new method of measuring flow velocity is effective in these experiments. The flow velocity obtained with the new measuring method is calibrated with the cross-correlation velocity. When the line sand velocity is less than 7m/s, the repeatability error of the measured velocity is less than ± 10%.
Materials demonstrating unusual large positive and negative thermal expansion are fascinating for their potential applications as high-precision microscale actuators and thermal expansion ...compensators for normal solids. However, manipulating molecular motion to execute huge thermal expansion of materials remains a formidable challenge. Here, we report a single-crystal Cu(II) complex exhibiting giant thermal expansion actuated by collective reorientation of imidazoliums. The circular molecular cations, which are rotationally disordered at a high temperature and statically ordered at a low temperature, demonstrate significant reorientation in the molecular planes. Such atypical molecular motion, revealed by variable-temperature single crystal X-ray diffraction and solid-state NMR analyses, drives an exceptionally large positive thermal expansion and a negative thermal expansion in a perpendicular direction of the crystal. The consequent large shape change (~10%) of bulk material, with remarkable durability, suggests that this complex is a strong candidate as a microscale thermal actuating material.
The genesis of intermediate intrusions is highly controversial, and one of the hot topics is whether they represent frozen melts or cumulates in the evolution of magmatic systems. Distinguishing ...accumulation from crystallization melt differentiated along the liquid line of descent is the key issue. The Paleoproterozoic intermediate intrusions in southern North China Craton provide an excellent case to decipher this issue. Multiple lines of evidence, including mineral textures, geochemistry as well as alphaMELTS modeling, indicate disequilibrium between whole‐rock and minerals, with melt extraction occurring at temperatures of 760°–820°C and with 10–40 wt.% of trapped melts. Effective water storage, revealed by amphibole and clinopyroxene hygrometers, plays a crucial role in promoting crystal‐melt segregation in pluton‐sized reservoirs in the upper crust. This study demonstrates that the accumulation in intermediate magmas can be identified even without evident complementary initial and extracted melts and provides deep insights into the genesis of intermediate continental crust.
Plain Language Summary
The genesis of intermediate rocks has long been controversial since they are analogs of the average composition of continental upper crust. The key topic is whether intermediate rocks represent frozen melts of intermediate magmas or crystal residues after melt extraction in the evolution of felsic magmatic systems. Here we carried out a comprehensive study on the Paleoproterozoic intermediate intrusions in the southern North China Craton, which is considered to have recorded the process of crystal accumulation and melt segregation in the shallow crust. Upon mineral texture, geochronologic, whole‐rock and mineral geochemical, and thermodynamic investigation, we propose that crystal accumulation and crystal‐melt segregation processes can be identified in intermediate magmas with the melt extraction temperatures and proportions of trapped melts recorded by zircon trace elements. Amphibole and clinopyroxene hygrometers revealed high water content of the melts, which likely decreased the viscosity of melts and facilitated effective cumulate‐melt segregation. This study provides a powerful reference to see through the accumulation in intermediate magmas, record the processes of crystal‐melt segregation, and definitively resolve the debate concerning the genesis of intermediate intrusions.
Key Points
Crystal accumulation in intermediate magmas can be identified by mineral texture and geochemistry
The effective water storage system in the reservoirs is key to promoting crystal‐melt segregation
Crystal‐melt segregation and accumulation are fundamental processes to form evolved continental upper crust
Zircons can retain a grain-scale record of granitoid compositional evolution that is accessible through microanalysis. In situ U–Pb, Hf and O isotope data yield new insights into the petrogenesis and ...evolution of the Neoproterozoic strongly peraluminous granitoids of the Jiangnan orogen (JO), southern China. A negative correlation of Th/U versus δ18O is found for most analyses. Some zircons from eastern JO granitoids show δ18O variations of 3–6‰ from core to rim, indicating a dramatic shift toward higher oxygen isotope values by voluminous partial melting of supracrustal rocks and signaling a transition from I-type-like to S-type-like magmas during the later stage of magmatic evolution. This mechanism provides a reasonable explanation why some granitoids have intermediate geochemical features between S-type and I-type granites. Hf isotope trends indicate that a larger proportion of mature continental crust was incorporated into the magma sources of the western JO granitoids, whereas more juvenile arc crust was incorporated into the eastern JO magmas. No significant depleted mantle-derived mafic magma was injected into the JO granitoid magmas. Instead, radiogenic Hf and Nd signatures in JO granitoids reflect incorporated juvenile arc crust and document crustal growth in southern China during the Early Neoproterozoic (ca. 900Ma). Thus, our zircon data suggest that strongly peraluminous granitoids, which are widely regarded as the products of orogenesis that primarily recycle evolved crust, can also record important information about early crustal growth.
► A negative correlation of Th/U versus δ18O resulted from AFC processes and late-magmatic fluids. ► Hf–O isotopes tend to be homogeneous at zircon rims for peraluminous granitoids. ► Zircons with clearly defined cores show large core–rim δ18O variations of 3–6‰. ► High-δ18O rims imply melting of supracrustal rocks and transition from I- to S-type-like magmas. ► Strongly peraluminous granitoids can also record important information about crustal growth.
The oceans are natural sources of atmospheric methane (CH₄), but the origin of excess CH₄ at the surface remains enigmatic. Incubation experiments were conducted in the western North Pacific (WNP) ...and its marginal seas (i.e., Yellow Sea and South China Sea SCS) to identify the degradation of methylphosphonate (MPn) to CH₄ in the oceans and the microbes associated with MPn-driven CH₄ production. In the coastal seawater of the Yellow Sea, CH₄ was observed to accumulate after MPn enrichment with a high MPn to CH₄ conversion efficiency (approximately 60%). Dissolved inorganic phosphorus (Pi) did not effectively restrict the microbial utilization of MPn in the eutrophic coastal waters. The results of 16S rRNA gene sequencing showed that Vibrio spp. were the dominant bacteria in the MPn-amended treatments. Moreover, several Vibrio isolates isolated from the coastal waters were found to produce CH₄ while growing in culture using MPn as the sole P source, thereby indicating that Vibrio spp. might be the major contributors to MPn-dependent CH₄ production. In oligotrophic areas, such as the SCS and WNP, CH₄ production from MPn metabolism was also observed in the surface seawater. In contrast to coastal waters, this pathway in oligotrophic areas is regulated by dissolved Pi availability. This work confirms that aerobic CH₄ formation from MPn degradation can occur both in eutrophic coastal waters and oligotrophic oceans driven by MPn-utilizing microorganisms (especially heterotrophic bacteria), which may have a significant impact on our understanding of the CH₄ and P cycles in global oceans.
The standard treatment for pediatric differentiated thyroid carcinoma (DTC) still requires consideration because of a lack of clinical evidence. The purpose of this study was to summarize the ...clinical experiences and explore the risk factors for post-operative recurrence through a retrospective analysis to develop better clinical strategies for pediatric DTC.
This study retrospectively analyzed children and adolescents with DTC who were treated between January 1999 and December 2014 at the Cancer Hospital, Chinese Academy of Medical Sciences. Clinicopathological results and outcomes were collected. A log-rank test of Kaplan-Meier curves and the Cox regression model were used to determine the factors associated with recurrence.
Data of 150 patients were collected in this study. During the follow-up, there was only one disease-related death. The recurrence rates at 3, 5, and 10 years were 13.6%, 18.7%, and 28.6%, respectively. There was a significant difference in the rate of recurrence according to age (P < 0.001), extrathyroidal extension (P < 0.001), lymph node metastasis (P = 0.023), and invasion of the trachea and esophageal wall (P = 0.004). Cox regression analysis demonstrated that age (P = 0.006) and extrathyroidal extension (P = 0.013) were significant dependent factors of post-operative recurrence.
The prognosis of DTC in children and adolescents is favorable. A close follow-up is recommended because of the high recurrence rate. A comparatively higher recurrence rate was observed in the younger age group, and new age-based divisions may be needed to conveniently evaluate the possibility of recurrence.
► ca 800–760Ma bimodal volcanic rocks in the eastern Jiangnan orogen (JO). ► Felsic rocks from the partial melting of juvenile arc crustal materials. ► Diversity of magma sources of the mafic rocks. ...► Dominant melting of newly-metasomatized lithospheric mantle implies the early significant subduction. ► Passive rifting resulted from post-orogenic extension in the JO has no direct relationship with rifting of Rodinia.
We present a systematic geochronological and geochemical study on ca 800–760Ma volcanic rocks in the eastern part of the Jiangnan orogen. The Xucun composite dykes are dated at ca 805Ma; the mafic components have OIB-like trace-element patterns and positive anomalies in Zr and Hf. The least-contaminated sample has relatively depleted Nd isotopic features, suggesting the Xucun mafic dykes may have been generated from the partial melting of OIB-like asthenosphere with later crustal contamination. The Xucun felsic dykes have decoupled Nd–Hf isotopes, and the Hf-isotope compositions of zircons indicate that the dykes may be derived from the partial melting of the early Neoproterozoic juvenile crustal materials, with minor incorporation of Paleoproterozoic crustal components. The ca 800–790Ma Shangshu volcanics include two compositional series: calc-alkaline and tholeiitic. The Shangshu calc-alkaline volcanics in the Minjiawu area have low abundances of LILE, HFSE and high Na2O contents and Sr/Y ratios, similar to adakitic rocks. The evident arc-like geochemical features and radiogenic Nd isotopes (ɛNd(t) values of +3.7 to +4.8) suggest that these rocks may have been generated from the partial melting of juvenile lithospheric mantle metasomatized by Na-rich melts released from the subducted slab. The tholeiitic mafic rocks from the Shangshu bimodal volcanics represent two different magma sources. The partial melting of metasomatized lithospheric mantle led to the formation of arc-like basalts with low TiO2 contents, negative anomalies in Zr and Hf, and high values of Mg# and ɛNd(t) (+6.2), whereas the partial melting of asthenospheric mantle generated volcanic rocks with high TiO2 contents and low positive ɛNd(t) (+1.4 to +2.7), without negative anomalies of Nb, Ta, Zr and Hf. The Shangshu felsic rocks were formed by the reworking of early Neoproterozoic juvenile arc crustal materials. The ca 760Ma mafic rocks from the Puling bimodal volcanics generally have low TiO2 contents (<0.9wt%), nearly flat REE distributions and arc-like trace-element patterns. They may have been generated from the high-degree partial melting of metasomatized lithospheric mantle. One sample has a high TiO2 content (2.41wt%) and high ɛNd(t) (+6.2), with overall OIB-like trace-element patterns, implying the local partial melting of asthenospheric mantle. The occurrence of significant volumes of bimodal volcanics in the eastern part of the Jiangnan orogen suggests an extensional setting in the period ca 800–760Ma. The evident partial melting of newly-metasomatized lithospheric mantle and subordinate partial melting of asthenosphere suggest that post-orogenic extension shortly after the Neoproterozoic orogenesis may be a better explanation for the genesis of the mid-Neoproterozoic magmatic rocks in the eastern part of the Jiangnan orogen. Post-orogenic extension may be diachronous along the whole orogenic belt, and probably has no direct relationship with the Rodinia rifting event. A more detailed model is presented to illustrate the evolution of the eastern part of the Jiangnan orogen.
Abstract
In subduction zones, materials on Earth’s surface can be transported to the deep crust or mantle, but the exact mechanisms and the nature of the recycled materials are not fully understood. ...Here, we report a set of migmatites from western Yangtze Block, China. These migmatites have similar bulk compositions as forearc sediments. Zircon age distributions and Hf–O isotopes indicate that the precursors of the sediments were predominantly derived from juvenile arc crust itself. Using phase equilibria modeling, we show that the sediments experienced high temperature-to-pressure ratio metamorphism and were most likely transported to deep arc crust by intracrustal thrust faults. By dating the magmatic zircon cores and overgrowth rims, we find that the entire rock cycle, from arc magmatism, to weathering at the surface, then to burial and remelting in the deep crust, took place within ~10 Myr. Our findings highlight thrust faults as an efficient recycling channel in compressional arcs and endogenic recycling as an important mechanism driving internal redistribution and differentiation of arc crust.
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